Method of more simple separation and collection of carbon nanotubes

Abstract

To provide a method for separating metallic CNT and semiconducting CNT by treating a CNT-containing gel or a CNT dispersion as combined with a gel, according to a physical separation means to thereby make semiconducting CNT exist in gel and metallic CNT exist in solution, in which the semiconducting CNT adsorbed by gel are collected in a more simplified manner not dissolving the gel. A CNT-containing gel or a CNT dispersion combined with a gel is treated according to a physical separation means of a centrifugal method, a freezing squeezing method, a diffusion method or a permeation method, to thereby make semiconducting CNT exist in gel and metallic CNT exist in solution so that the metallic CNT and the semiconducting CNT are separated from each other, and further, a suitable eluent is made to react on the gel that adsorbs semiconducting CNT to elute the semiconducting CNT from the gel.

The invention claimed is: 
     
       1. A method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes, which comprises:
 centrifuging a carbon nanotubes-containing gel with a centrifuge to obtain (1) a solution fraction containing metallic carbon nanotubes in the solution eluted from the gel through centrifugation, and (2) a gel fraction containing semiconducting carbon nanotubes in the gel compressed by centrifugation, 
 separating (1) the solution fraction containing metallic carbon nanotubes and (2) the gel fraction containing semiconducting carbon nanotubes from each other, and 
 adding an eluent to (2) the gel fraction containing semiconducting carbon nanotubes to thereby elute the semiconducting carbon nanotubes from the gel adsorbing the semiconducting carbon nanotubes. 
 
     
     
       2. A method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes, which comprises:
 freezing a carbon nanotubes-containing gel, 
 then squeezing the gel after thawed, to separate it into (1) a solution containing metallic carbon nanotubes in the solution eluted from the gel, and (2) a gel containing semiconducting carbon nanotubes in the squeezed gel, and 
 adding an eluent to (2) the gel containing semiconducting carbon nanotubes to thereby elute the semiconducting carbon nanotubes from the gel adsorbing the semiconducting carbon nanotubes. 
 
     
     
       3. A method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes, which comprises:
 dipping a carbon nanotubes-containing gel in a solution to obtain (1) a metallic carbon nanotubes-containing solution formed by diffusing and eluting metallic carbon nanotubes into the solution from the gel, and (2) a semiconducting carbon nanotubes-containing gel, 
 then separating (1) the metallic carbon nanotubes-containing solution and (2) the semiconducting carbon nanotubes-containing gel from each other, and 
 adding an eluent to (2) the semiconducting carbon nanotubes-containing gel to thereby elute the semiconducting carbon nanotubes from the gel adsorbing the semiconducting carbon nanotubes. 
 
     
     
       4. A method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes, which comprises:
 mixing a gel and a carbon nanotube dispersion to thereby make semiconducting carbon nanotubes permeate into the gel and concentrate metallic carbon nanotubes in solution, 
 then taking out and separating the metallic carbon nanotubes-containing solution from the carbon nanotubes-containing gel, and 
 adding an eluent to the carbon nanotubes-containing gel, thereby eluting the semiconducting carbon nanotubes from the gel adsorbing the semiconducting carbon nanotubes. 
 
     
     
       5. A method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes, which comprises:
 making a carbon nanotube dispersion pass through a gel to thereby make the gel adsorb semiconducting carbon nanotubes, 
 then eluting and separating the unadsorbed metallic carbon nanotubes, and 
 adding an eluent to the gel from which the solution has been separated, thereby eluting the semiconducting carbon nanotubes from the gel adsorbing the semiconducting carbon nanotubes. 
 
     
     
       6. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in any one of  claims 1  to  5 , wherein in the elution step of eluting the semiconducting carbon nanotubes from the gel, the eluent contains a surfactant of a type that differs from that of the surfactant used for separation. 
     
     
       7. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in  claim 6 , wherein the surfactant contained in the eluent is sodium deoxycholate, sodium cholate, sodium dodecylbenzenesulfonate, Tween-20 or Triton X-100. 
     
     
       8. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in any one of  claims 1  to  5 , wherein in the elution step of eluting the semiconducting carbon nanotubes from the gel, the eluent contains a surfactant of the same type as that of the surfactant used for separation. 
     
     
       9. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in  claim 8 , wherein the surfactant contained in the eluent has a higher concentration than that of the surfactant used for separation. 
     
     
       10. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in any one of  claims 1  to  3 , wherein the carbon nanotubes-containing gel is prepared by previously dispersing and solubilizing carbon nanotubes with a surfactant, and then ultrasonically treating them to make the carbon nanotubes exist in the gel in a dispersed and isolated state. 
     
     
       11. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in  claim 4  or  5 , wherein the carbon nanotube dispersion is prepared by previously dispersing and solubilizing carbon nanotubes with a surfactant, and then ultrasonically treating them to make the carbon nanotubes dispersed and isolated in the dispersion. 
     
     
       12. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in  claim 10 , wherein the surfactant is an anionic surfactant or an amphoteric surfactant. 
     
     
       13. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in  claim 12 , wherein the anionic surfactant is alkyl sulfate salt, sodium dodecanesulfonate, dodecanoylsarcosine sodium, sodium dodecanoate, or sodium cholate. 
     
     
       14. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in  claim 13 , wherein the alkyl sulfate salt is sodium dodecyl sulfate, sodium decyl sulfate or sodium tetradecyl sulfate. 
     
     
       15. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in  claim 12 , wherein the amphoteric surfactant is n-dodecylphosphocholine. 
     
     
       16. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in  claim 11 , wherein the surfactant is an anionic surfactant or an amphoteric surfactant. 
     
     
       17. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in  claim 16 , wherein the anionic surfactant is alkyl sulfate salt, sodium dodecanesulfonate, dodecanoylsarcosine sodium, sodium dodecanoate, or sodium cholate. 
     
     
       18. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in  claim 17 , wherein the alkyl sulfate salt is sodium dodecyl sulfate, sodium decyl sulfate or sodium tetradecyl sulfate. 
     
     
       19. The method for separating and collecting metallic carbon nanotubes and semiconducting carbon nanotubes as claimed in  claim 16 , wherein the amphoteric surfactant is n-dodecylphosphocholine.